SpacetimeDB/crates/codegen/examples/regen-csharp-moduledef.rs

//! This script is used to generate the C# bindings for the `RawModuleDef` type.
//! Run `cargo run --example regen-csharp-moduledef` to update C# bindings whenever the module definition changes.

use fs_err as fs;
use regex::Regex;
use spacetimedb_codegen::{csharp, generate, CodegenOptions, OutputFile};
use spacetimedb_lib::{RawModuleDef, RawModuleDefV8};
use spacetimedb_schema::def::ModuleDef;
use std::path::Path;
use std::sync::OnceLock;

macro_rules! regex_replace {
    ($value:expr, $re:expr, $replace:expr) => {{
        static RE: OnceLock<Regex> = OnceLock::new();
        RE.get_or_init(|| Regex::new($re).unwrap())
            .replace_all($value, $replace)
    }};
}

fn main() -> anyhow::Result<()> {
    let module = RawModuleDefV8::with_builder(|module| {
        module.add_type::<RawModuleDef>();
    });

    let dir = &Path::new(concat!(
        env!("CARGO_MANIFEST_DIR"),
        "/../bindings-csharp/Runtime/Internal/Autogen"
    ))
    .canonicalize()?;

    fs::remove_dir_all(dir)?;
    fs::create_dir(dir)?;

    let module: ModuleDef = module.try_into()?;
    generate(
        &module,
        &csharp::Csharp {
            namespace: "SpacetimeDB.Internal",
        },
        &CodegenOptions::default(),
    )
    .into_iter()
    .try_for_each(|OutputFile { filename, code }| {
        // Skip anything but raw types (in particular, this will skip top-level SpacetimeDBClient.g.cs which we don't need).
        let Some(filename) = filename.strip_prefix("Types/") else {
            return Ok(());
        };

        // Someday we might replace custom BSATN types with autogenerated ones as well,
        // but for now they're not very large and our copies are somewhat more optimised.
        //
        // Ignore those types and replace their references with our own with plain old regexes.
        if filename == "AlgebraicType.g.cs" || filename.starts_with("SumType") || filename.starts_with("ProductType") {
            return Ok(());
        }

        // CaseConversionPolicy is part of the public API — move it to
        // the SpacetimeDB namespace so users don't have to write
        // SpacetimeDB.Internal.CaseConversionPolicy.
        let code = if filename == "CaseConversionPolicy.g.cs" {
            regex_replace!(&code, r"namespace SpacetimeDB\.Internal", "namespace SpacetimeDB")
        } else {
            // In other autogen files, qualify the type name in type position
            // (before a space+identifier) so it resolves after the namespace move.
            // The pattern "CaseConversionPolicy CaseConversionPolicy" becomes
            // "SpacetimeDB.CaseConversionPolicy CaseConversionPolicy".
            regex_replace!(
                &code,
                r"\bCaseConversionPolicy(\s+)CaseConversionPolicy\b",
                "SpacetimeDB.CaseConversionPolicy${1}CaseConversionPolicy"
            )
        };

        let code = regex_replace!(&code, r"\bAlgebraicType\b", "SpacetimeDB.BSATN.$0");
        let code = regex_replace!(
            &code,
            r"\b(ProductTypeElement|SumTypeVariant)\b",
            "SpacetimeDB.BSATN.AggregateElement"
        );
        let code = regex_replace!(
            &code,
            r"\b(Product|Sum)Type\b",
            "List<SpacetimeDB.BSATN.AggregateElement>"
        );

        fs::write(dir.join(filename), code.as_ref())
    })?;

    Ok(())
}